Question

According to the genetic theory of C.B. which is correct for the AAA+XXY condition of A. A. A. A. Drosophila:
B. Super male
C. Super female
D. Intersex
E. Normal male but sterile.

Answer 1

Hint: Drosophila sp. Comprises four pairs of chromosomes. Among the four pairs, 1 pair are sex chromosomes and 3 pairs are autosomes. The genotypic expression of female Drosophila is XX+AA and the genotypic expression of the male Drosophila is XY+AA.

Complete answer:
The sex determination of Drosophila sp is done by the ratio of sex chromosome (X) and autosome(AA). There are four types of phenotypic expressions found in Drosophila sp. These are given below:
> Male
> Female
> Sterile male
> Intersex.
The rules of sex determination in Drosophila sp:
In the case of diploid:
If the ratio of X chromosomes and autosome is 1, it will phenotypically appear as the female.

XXAA

X:A = 1

Female

If the ratio of X chromosomes and autosomes is .5, a male fly will appear.
X:A= .5

XYAA

X:A= .5

Male

If the Y chromosome is absent and the X: A ratio is .5, the sterile male will appear.

XOAA

X:A = .5

Sterile male

In the case of aneuploid:
More than 2 X chromosomes with the X: A ratio 1 will appear as a female.

XXXAAA

X:A= 1

Female

More two X chromosomes with the X: A ratio .67 is intersex

XXYAAA

X:A = .67

Intersex

One X with the X: A ratio .33 will appear male.

XYYAAA

X:A =0.33

Male

Note: Sxl gene in Drosophila is responsible for determining the sex. When the X: A ratio is 1, the Sxl gene is activated and starts to encode a protein that results in a phenotypically female fly. When the ratio of the X chromosome and autosome is .5, it synthesizes a nonfunctional Sxl protein which leads to a male fly.